Conventional cocoa powder hardly dissolves. It readily forms masses if directly added to hot water or hot milk. For drinking, therefore, cocoa powder must be preliminarily kneaded with a small amount of warm water or warm milk so as not to form masses and then diluted to a desired concentration. On the other hand, compounded cocoa, which is prepared from cocoa powder, sugar, powdered milk, etc., can easily be granulated usually by wet granulation. Compounded cocoa containing soluble ingredients, such as sugar, in a large proportion, is easy to dissolve. Furthermore, compounded cocoa available on the market and which is ready to dissolve even in cold milk or water can be prepared by coating cocoa powder with an emulsifier, such as lecithin, followed by granulating as described, for example, in JP-A-62-272941 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"). Thus, various techniques have been proposed relating to the solubility of compounded cocoa, but a technique for making cocoa powder itself soluble has not yet been developed.
The reason why cocoa powder hardly dissolves and readily forms masses upon dissolving seems to reside in that cocoa powder (1) has a high insoluble content, such as fiber, (2) has a fat (cacao butter) content of 8% or more, and (3) has a finely powdered form so as not to impart a rough texture to the mouth. Granulation of cocoa powder could be a solution to the problem of poor solubility, but it is very difficult to apply granulating techniques commonly employed in the preparation of compounded cocoa to cocoa powder itself. Although mere granulation of cocoa powder is possible by adopting some known techniques, such as extrusion granulation or compression granulation, the resulting granules are too hard to be dispersed and disintegrated on stirring in water, etc., and are therefore not practical.